Carnie Wilson's War: Weight Gain After Gastric Bypass

And while a few patients regain a large percentage of their original weight back, Dr. Anita Courcoulas, chief of minimally invasive bariatric and general surgery at the University of Pittsburgh Medical Center, says that most of those who have gone through the surgery will experience some weight gain after the bulk of their post-surgery loss.

"Most patients experience something I call 'the creep,'" she said. "They creep up another five to 10 pounds. Eighty percent will experience this creep and level out again, but about 20 percent will continue to creep up."

It turns out that caloric restriction is just one part of the equation, although a large part. And reducing the space in your stomach into which your meals can fit to the size of a large walnut is a particularly effective way to cut hunger and jump-start weight loss for morbidly obese individuals.

The most rapid phase of weight loss after surgery occurs during the first year. After this, the rate of weight loss will slow. And after two years, the patient has reached a new "set point" in terms of weight.

From here, biology can reassert itself. Courcoulas says the tiny pouch that serves as the new stomach expands slightly in most patients, perhaps increasing in size between 10 percent and 15 percent. If a stretch of intestine has been removed through surgery, the remaining portion may become more efficient in absorbing calories. For most, these changes result in just a slight "bounce" to a modestly higher weight.

But for some, this plateau period represents a danger zone. If a patient's eating and exercise habits have evolved, they can maintain this new weight. But if they have not, excess eating can cause what remains of the stomach to stretch significantly to accommodate more food -- thus leading to weight gain.

"If you tend to keep pushing yourself, taking one extra bite with every meal, then you can stretch the pouch," Jones said. "Over time you will eat more and more."